Electric switch



Ti,694,223 G N. LEMMON ELECTRIC SWITCH Filed June 19, 1925 2 Sheets-Sheet 1 'I I hn INVENTOR GEORGE. IV- LE /won ATTORNEYS Dec. 4, 1928.

1,694,223 G. N. LEMMON ELECTRIC SWITCH Filed June 19, 1925 2 Sheets-Sheet 2 construction that Pas ed Dec. 4, 192a.

UNITED STATES PATENT OFFICE.

GEORGIA, ABSIGNOR TO BALT MANUFACTURING 60., OF ATLANTA, GEORGIA, A CORPORATION OI GEORGIA.

' mc'rmc Application filed June 19 1983. Serial No. 648,887.

My invention relates to electric switches and particularly heavy current. vention are first, to provide a switch of such the switch contacts are preserved from injury incident to are formation on the opening of the switch; second, to automatically reduce the current at the moment the switch'is opened; third, to prevent shock to the electrical system incident to a sudden interruption of t e circuit; fourth, to' provide means which automatically reduces the current flow and then interrupts the circuit; fifth, to provide a protective shunt around the main switch contacts and to arrange in that shunt automatic resistance and interrupter elements; sixth, various features hereinafter described or illustrated in the accompanying drawings, in whichig. 1 is. a more or less diagrammatic verticalsection through a switch in which my invention is illustratively embodied;

Fi s. 2 and 3 are similar views showing the switc in different positions; and a Fig. 4 is a similar view of a modification. Various forms of oil switches or oil circuitbreakers are now in use in whichone or more contacts are opened under oil, and various methods are used to cool the are so formed. For lines of small current capacity these switches operate very satisfactorily. But for interruptin the flow of heavy current, oil switches are $11 ject to several serious objec tions. For instance, the oil itself becomes somewhat carbonized in the presence of an arc and therefore deteriorates as an insulator. Again, there is the omnipresent danger that an are formed beneath the surface of the oil will cause an explosion of the oil. Moreover, since oil is in itself an insulating medium of high value, when the switch opens the oil tends to form immediately an insulating barrier between the separating contacts. This instantaneous shut-ofl' of the electric current causes a heavy reaction on the-line as the electromagnetic field of the system collapses, and the energy becomes largely concentrated at the point where the flow of current is interrupted by the oil.

When a vaporizable fluid such as water, a water solution, or a liquid which functions similarly, is used as a conductor for heavy electric currents, its resistance is such that if the cross sectional area. of the liquid is not to switches for breaking Among the objects of my inis a circuit, the

too great, some or all of the liquid vaporizes. This vapor hasa much higher resistance than the liquid itself. ..The longer the current flows, the more liquid becomes vaporized. A constantly increasing resistance is thereby interposed in the circuits. The period of time within which the resistance is increasmg varies with the current and the shape 'of the water column. For the-present purpose it is preferably several cycles. During this period the-current is steadily decreasing in value, and when sufliciently reduced the circuit may be positively and completely opened w thout danger of heavy arc formation, and without serious shock to-the system. The present invention utilizes this characteristic and provides a novel method and apparatus by which the circuit may be completely opened at the moment whenthe current has been appropriately reduced. While the invention is not limited to this iitility and its application to oil switches, I have employed the latter to illustrate more or less diagrammatically a practical embodiment thereof.

Thus, as here shown, the switch comprises an oil container or casing 15 of any suitable size and shape, filled to an appropriate level, with oil 16. Submerged therein are the fixed contacts 17 and 18 of the switch connected respectively to the incoming and outgoing line leads 19 and 20. Bushings 21 and 22 insulate the leads from the top 23 of the easing, through which they pass. Arranged within the casingand cooperating with the fixed contacts 17 and 18 is the switch bar 24 which carries the cooperating contacts 25 and 26. The switch actuating rod 27 is insulated in any appropriate fashion, from the switch bar, as by an insulating bushing 28, and serves to lift the bar to close the switch, and vice versa.

Shunted around the main switch contacts, branches 29 and 30 of which enter the switch chamber through bushings 31 and 32, and are connected to auxiliary switch contacts 33 and 34, also submerged in the oil 16.- The switch bar 24 is extended laterally and carries cooperating switch contacts 35 and 36 mounted on rods 37 and 38 which slide through metal sleeves 39 and 40 in the bar 24. Interposed between the contacts 33 and 34-and the switch bar 24, and surrounding the rods 37 and 38 are coil springs 41 and 42. Below the switch bar and also ill surrounding the rods 37 and 38 are other coil springs 43 and 44 confined by the heads 45 and 46 at the lower ends of the rods.

Arranged in the shunt leads 29 and 30 between the contacts 33 and 34 respectively, and the line leads 19 and 20 respectively, are containers 47 and 48, the bodies of which are of insulating material. The containers are closed at their opposite ends by metal caps 49 and 50 which form sealed joints with the ends of the casings and serve to hold within the latter a supply of vaporizable liquid, such as water 51. The interior of each chamber is divided longitudinally into compartments 52 and 53 by a barrier 54, pierced by a passage 55 below the water level, through which communication is established between the two chambers. The passage may be of any appropriate cross section and length, and may be so located that it does not wholly lie below the water level provided the water level is above the bottom of the passage.

Appropriately arranged in the shunt circuit are electromagnets 56 and 57 through which the shunt currentflows. Ashere shown they are arranged just above the fixed contacts 33 and 34, and serve, when energized, to hold the auxiliary switch contacts 35 and 36 in circuit-closing position. For this purpose the rods 37 and 38 may be of soft iron or other magnetic material-and they may be extended, if desired, through the contacts 35 and 36 into the axis of the coils. Or the rods may be of non-magnetic material, and the contacts 35 and 36 may be formed, in part, of magnetic; material.

In the closed position of the switch illustrated in Fig. 1, when the main contacts 25 and 26 on the switch bar 24 are in engagement with the fixed contacts 17 and 18, the shunt circuit is also closed between the contacts 33 and 35 on the one hand, and 34 and 36 on the other hand, the current passing through the water 51 in each chamber 47 and 48. In this position of the parts the springs 41-42 are compressed. Upon the opening of the main switch by the depression of the rod 27, the main contacts 17, 25 and 18, 26 part, as illustrated in Fig. 2, before the contacts of the auxiliary shunt switch separate, since the springs 41 and 42 expand and hold these contacts in engagement as the switch bar 44 is lowered. Immediately upon the parting of the main contacts 17, 25 and 18, 26, the shunt circuit carries all of the current, and the latter flowing therethrough fully energizes the electromagnets 56 and 57. The contacts 35 and 36 are consequently held in engagement with 24 moves further downward and stresses the springs 43 and 44. The shunt circuit is thus maintained and the current flows through the liquid 51. The water in the constricted passageway 55 is vaporized, and as illustrated in Fig. 3, interposes a vapor resistance 58 to the flow of current. This resistance so reduces the current and consequently the pull of the magnets 56 and 57, that the latter are unable to maintain the contacts 35 and 36 in engagement with the contacts 33 and 34, against the stress of the springs 43 and 44. At the moment therefore, when the current is reduced by the interposed vapor resistance 58, the auxiliary switch automatically opens and thus completely interrupts the circuit.

It will be obvious that upon the opening of the main switch, the contacts 17, 25 and 18, 26 separate without arc formation, since the shunt circuit provides a path for the flow of current at this period of operation. A destructive arc is thus avoided at the main contacts. While the heavy current flows through the shunt circuit, the latter is maintained closed by the pull of the magnets 56 and 57, but when the liquid vaporizes, interposing the resistance vapor 58, the current flowing through the shunt is reduced, the electro-magnets weakened, and at the moment when the current flow is low the shunt switch opens without a destructive are being established beneath the oil surface.

When the flow of the current through the shunt circuit ceases, the vapor in the chamber 48 condenses, the liquid flows again into the passage 55, and normal conditions in the chamber are re-established. It is obvious that a single chamber 48 in the shunt circuit may suflice under some conditions.

A modification is illustrated in Fig. 4, in which the shunt circuit includes only the electrolyte resistance element 470. As here shown the main switch 59 and the auxiliary switch 60 are arranged in series and are in general of like construction, but the switch rod 61 of the auxiliary switch has associated therewith a switch opening spring 62, which is stressed when the switch is closed. A latch lug 63 on the rod is engaged by the latch 64 governed by the electro-magnet 65, which is constantly in the circuit.

Upon the opening of the main switch 59, the current flows through the shunt 66 in which the element 470 is arranged. As soon as the vapor resistance is interposed in the circuit,'the current flowing through the electro-magnet is so reduced detent 64 and releases the rod 61 of the auxiliary switch 60, which nowopens under the action of the spring 62.

My underlying thought is to provide a secondary path for the current through which it flows when the main switch is opened and to arrange in that path a liquid which the the contacts 33 and 34, while the switch bar current vaporizes, the vapor affording a high resistance to current flow, and associating therewith means automatically operative to completel open the circuit when the current flow has een suiiiciently diminished by the vapor resistance to render arc formation unimportant. The feature of self-restoration of that it frees the either-theair-break or the oil-break type. If the main switch is of the air-break type, and

the resistance unit to normal condition is connection with oil switches, since this type 1s one which-is extensively ,used,rit will understood of course that th applicable to switches of the us, for example, the auxiliary switch may well be of the air-break type, held in closed position by a magnet or by amagnetically released trip device, but w ich opens. when the current flowing is reduced by the resistance of the vapor in the secondary circuit. If the main switch is of the air-break type, the injury to its contacts from are formation on opening, is entirely eliminated. It is thus possible this character,

e invention is and the auxiliary switch of the auxiliary switch of the oilrbreak type, the final circuit rupture at reduced current flow occurs under particularly safe and effective conditions;

Again, it is not 11 ary circuit be established prior-to the opening movement of the-main switch. Thus, the

.main switch may have associated therewith contacts which are normally open when the main switch 'is' closed, but which establish the secondary circuit during the opening movement of the main switch but before the main switch contacts part. Or there may be an independent switch which is operated to close the secondary circuit ahead of the opening of the mainswitch. These are ob- VlOllS variants of the underlying conception of my invention.

Wlth the foregoing indication of some of the various applications of the invention, and with the understanding that construction are subject to wide variation, as well as the character of the vaporizing fluid, I claim as my invention- 1. Circuit interrupting means comprising a main switch and an auxiliary switch, a secondary path for the current controlled only by the auxiliary switch, a vaporizable liquid air-break type.

to make the main switch of i that the second thedetails of ow of current therethrough on the open 1 mg of the main switch and to interpose a reby'the auxilia switch, a vaporizable liquid in series with t e auxiliary switch in the secondary path and adapted to be vaporized by the flow of current therethrough on the'open-.

ing of the main switch and to interpose a resistance vapor in the secondary path, and means for automatically opening the auxilia'ry switch when the current flow is reduced ythe vapor resistance, together with electromagnetic means fordetaining the auxiliary switch in: closed position until the current flow is sufiiciently reduced by the interposed vapor resistance.

3. Circuit interrupting means comprising a main switch and an auxiliary switch, a sec-7 ondary path for the current. controlled only by t e auxiliary switch, a self-restoring vaporizable liquid in the seconda path and adapted to be vaporized by the ll ow of current therethrough on the opening of the main switch and to ihterpose a resistance vapor in the secondary path, and means for automatically opening the auxilliary switch when the current flow is reduced by the-vapor resistance.

4. Circuit interrupting means comprising a main switch and an auxiliary switch, an insulating liquid submer g theswitch contacts, a secondary pathv or the current controlled by the auxiliary switch, a' vaporizable liquid in series with the auxiliary switch in the secondary path and adapted to be vaporthe flow of current therethrou h on ized by the opening of the main switch and to interpose a resistance vapor in the secondary path,

an independent container for said vaporizable liquid, and means for automatically opening the auxiliary switch when the currentfiow is, reduced by the vapor resistance.

5. Circuit interrupting means comprising a main switch and an auxiliary switch, an insulating liquid submerging the switch contacts, a secondary path for the current controlled by the aux liary, switch, a vaporizable liquid in series with the auxiliary switch in the secondary path and adapted to be vaporized bythe flow of current therethrough on the opening'of the main switch and to interpo'se aresistance vapor in the secondary path an independent container'for said vaporizable liquid, said container-being exterior to the non-conducting liquid in which the switch contacts are submerged, and means -for' automatically opening the auxiliary switch when the current flow is reduced by the "vapor resistance.

- In testimony whereof I have name to this specification.

GEORGE N. LEMMON.

signed my 

